Abstract

By using a scanning tunneling microscope (STM) we investigated the local ferroelectric behaviour of copolymer P(VDF-TrFE) films of various compositions and crystallinity. By means of the STM we examined locally the variation of the film thickness as a function of the poling voltage (a newly developed microscopic adaptation of the so-called “butterfly” technique), achieving an accuracy of better than 1 Å in height and a lateral resolution in the nanometer range. We could clearly distinguish the different ferroelectric switching behaviour of the amorphous and crystalline domains. In addition, we were able to detect the switching of individual crystallites, the analogue to the Barkhausen-effect in ferromagnetic materials, which has not been seen so far in ferroelectric systems. Finally, our observation of a spread-out but strong ferroelectric switching also in the amorphous regions of sample is not compatible with the current theoretical structural model of a strictly non-ferroelectric amorphous phase enclosing the ferroelectric crystallites.

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